Process of and apparatus for treating minerals



PROCESS OF AND APPARATUS FOR TREATING MINERALS File'd. 1925 2 Sheets-Sheeixl w Kin/Lay JToc/rTo/Y INVENTOR.

BY 5% a V I i 7 ATTORNEY.

PROCESS OF AND APPARATUS FOR TREATING MINERALS 2 Sheets-Sheet 2 Filed July 20. 1925 0 INVENTOR.

ATTORNEY.

Patenited es. 2i, 125$ MOKINLEY STOCKTON, OF LOMPOC, OALIFORN IA,'ASSIGNOR TO THE CELI'IE COMPhllTY, Oh LOS ANGELES, CALIFORNIA, A CORPORATION OF DELAWARE.

PROCESS OF AND APPARATUS FOR TREATING MINERALS.

Application filed July 20,

This invention pertains to the art. of milling; disintegrating or crushing of mineral bodies to a state of fine division, a classification or separation of such milled mineral and alsoprovides for the drying, dehydration and calcination, or both, of such minerals. I

The principal object of this invention is to disclose a'method of milling a mineral, drying or calcining such milled mineral, and then separating the milled product into desired grades of fineness without the loss of the exceedingly fine. particles produced by the milling operation. This method or process of operation may be effected in relatively simple, inexpensive apparatus, also disclosed and claimed by me.

Many minerals and clays which it is de-. sired to dry and mill, such as, for example, diatomaceous earth, kieselguhr or in'fusoria] earth, or such' earths combined with clay, contain high amounts of absorbed. or combined' water or both forms of moisture. In

the case of diatomaceous earth, the raw or crude mineral contains as much as 65% absorbed moisture. It has been found that most porous minerals'i n lump form, or minerals originally found with a high moisture content, resist a\ drying operation, after a portion of'the water has been-removed, be-

.cause of the fact that the outer surfaces of the material insulate the inner portions, and

thereby prevent the rapid penetration of drying heat. It is, therefore, seen that if the drying operation isperformed on minerals in a finely divided form, the drying heat may be applied to much greater benefit. The most effective drying operation, therefore, is thatin which the mineral material is first ground to a suitable state of division and then exposed to a heated medium or gas so that each individual particle is surrounded by the heating or drying medium; The latter mode of opera tion has been used on certain particular products by blowing the powdered or gr'anu lar product into a receptacle or chamber, a'

heated gas being generally used. There has been difiiculty experienced, however, in the subsequent separation of the powdered material from the gas. The dust problems arisjug from this method necessitating the use without the loss of vthe finest constituents,-

1925. Serial No. 44.896.

. a in of ,electrical dust collectors, sp tems and the like.

It is acknowledged that certain units of equipment similar to those comprising the apparatus herein disclosed 'have been disclosed by the prior art, for example, conicalair separating chambers have been used for such purpose, but to the best of my knowledge, such units have never been connected, as shown by me, nor was it possible to heat, separate, and mill or disintegrate a mineral in a closed circuit, and eliminate the loss of 5 finely disintegrated constituents;

The present invention discloses a process of drying' mineral materials in a finely divided form (containing moisture) in a current of heated gas or other fluid and then separating the dried material from said gas in suitable air separating apparatus, the dust being recovered by bringing it in contact with the moist or wet material just entering the process on which the dust is absorbed and retained.- In this manner a dust loss. is not created and the use of expensive or elaborate dust collecting machinery is obdated, theform of apparatus which has been found to be adapted to the process being, comparatively simple and inexpensive, My process is particularly adapted to-the milling, drying, and separating operations encountered in the treatment of diatomaceous' earth, kieselguhr or. infusorial earth, or the like. It has been used with entire success in the production of powdered grades of diatomaceous earth of such fineness that'only 1-5% is left on a 1'50-mesh screen, while about 20-40% of the material is less than 0.001 mm. in size. Inasmuch as the dried, powdered diatomaceous earth in this state of division weighsbut 8 to 10 lbs. per cu. ft. great dificulty. had hitherto been encountered in separating the dust of such product, from the gas or other fluid used in conveying 0r separating apparatus.

The accompanying drawings give a diagrammatic illustration of my process. and

one modification thereof andat the same time disclose an apparatus which may be used in its operation. Fig. 1 shows a process in -which a. mineral material is disintegrated, dried, and separated into various grades of fineness. Fig. 2 shows a modification of theprocess in which a mineral margrefractory tile, etc.

rial is disintegrated, dried, calcined and separated into various grades of fineness.

In Fig. 1 the raw or crude mineral (containing moisture) is fed from a suitable bin 4 to a preliminary milling machine 5 which in this case may be spiked rolls. The partly crushed mineral may then be fed through a tourniquet, scroll, or other feeding device 6 into an enclosed milling or disintegrating apparatus 7 of any appropriate design, for example, a swing hammer mill, from which the milled material is discharged by suitable means such as pipe means 8 into a fan, blower, or disintegrator ,9 adapted to the conditions. This blower or disintegrator discharges the milled material through pipe means 10 into an air separator or cyclone 1 which is equipped with an outlet means 2 through which all exce:s air or gas or other fluid may be discharged. The base of the cyclone or separator 1 into which the milled mineral settles, may be provided with a tourniquet, scroll, or other feeding device 12 which discharges from means 13 into suitable pipe or cylindrical means 14, of requisite length andwhich may be made of cast iron, A furnace, heater, or other suitable source of heated air, gas, or other fluid, for example, waste heat. from another operation (provided such gas is at a temperature above 212 F.), indicated at 15 discharges into means 14c and the moist, -milled material from cyclone 1 is thereby surrounded in means 14 with a heated gas or drying medium. This mixture of milled material and gas is discharged into a blower or disintegrator 16 which in turn discharges through means 17 into' a second cyclone air separator or other suitable device 2. The discharge 18 from this second cyclone leads back to the milling or disintegrating apparatus 7 and thereby forms a closed circuit.

The above process and apparatus pertain directly to my invention and the dried and milled mineral may then be discharged through suitable feeding device 19 from the bottom of cyclone 2 but inasmuch as it has been heated during the drying operation in its passage through means 14, blower 16, and means 17, it may be desirable to cool said material before bagging or otherwise preparing the material for shipment. The milled and dried mineral may he, therefore, discharged from the base of cyclone 2 through suitable feeding mechanism such as a tourniquet 19 into means 20 leading into pipe means 21, provided with an inlet for cold air as indicated at 22. The finely divided and dried mineral matter is then sucked into a fan or impeller 23 of suitable design, and discharged through means 24 into cyclone 3, from which the coarser material is discharged through a valve, -or scroll, or tourniquet, etc, 29, into a suitable container or bin from which it may be removed through means 31 and sacked, bagged, or otherwise prepared for shipment. Air-containing exceedingly fine particles ordust,

tainers, through which the air is blown, the

dust being left on the interior-of said tubular membranes. Eventually the dust falls to the base 28 of said stocking dust collector and may be withdrawn therefrom periodically and also bagged or otherwise prepared for shipment as a' distinct and exceedingly fine grade of material.

The temperatures of the gases discharged into the atmosphere from the separating chamber 1 must not be too high, else a certain amount of very finely disintegrated material is lost through this outlet. The temperature of the exhaust gases at which the most effective operation takes place varies with the percentage of moisture in the crude or raw material being treated, the temperature to which the material is heated, the percentage of moisture in the material entering that separating chamber which exhausts into the atmosphere, and the velocity of the gases. For example, in the manufacture of disintegrated or finely divided diatomaceous earth from natural diatomaceous earth, which originally contained 40% free moisture, it was found that if the disintegrated mate'rialentering the air separating chamher 1 contained less than about 20% moisture, the exhaust gases 11 would show a loss of dust, while when the moisture content was greater, say 25%, there was no dust loss.

This was true under identical conditions; that is, the degree of milling and velocity of gases was kept constant. Temperature of the gases going through blower 16 were ap proximately 500 F. while the gases being returned to the primary disintegrator 7 were about 225 so that some drying action also took place in means 8, 9, and 10. Supplies of heated gas may be introduced at disintegrator 7 or to pipe means 8, in addition to the gases introduced by heater or other source 15, whenever the material being fed into the system at 4 contains very large quantities of moisture' Referring to Fig. 1, it is seen that the'exhaust 18 from chamber 2' contains dust which is absorbed 01' retained by the moist material disintegrated in the mill 7 and that there is no dust loss from exhaust 11 fromv chamber l, by reason of the moisture present in the material at this stage. v

Fig. 2 refers to a modification of my proc ess in which the temperatures to which the materials are heated are relatively high, for example, temperatures. about 1400 F. or 1800 F. or higher may be reached in the calcining zone. This modification also cmbraces a step in which the heated gases from the calcining zone are: passed through the previous zones and the heat contained in such heatec gases is used in drying themineral before it reaches. the calcining zone. In this modification also dust loss is prevented in much the same manner as-described' 1n Fig.

1. The calcination disclosed by the followwhich may be a scroll or'belt conveyor), to

an' enclosed disintegrating apparatus 58 which may he a swing hammer mill or the like. The disintegrated mineral is then passed by suitable pipe means 59 through a fan or impeller 6Q (which maybe so 'designed as to give a certain amount of disintegrating action), through pipe means 61 to a suitable air separating chamber 51. The exhaust 51 fromsaid air separating chamber discharges into the atmosphere While the disintegrated material discharges from the air separating chamber 51 through a tourniquet,

scroll, or other suitable means 62 into and through pipe means 63 into pipe meansfil,

taining the disintegrator 57.

which lead to a fan or impeller 65. The last.

mentioned fan discharges through pipe means 66 into a secondary air separating chamber 52. The gas containing fine par-' ticles of matter is discharged from the air separating chamber. 52 through pipe means 67 and lead back to the closed chamber con.-

The disintegrated material from air separating chamber 52 is discharged through a suitable feeding mechanism 68which may be a tourniquet, scroll, or the like, into pipe means 69, which discharge directly into a suitable chamber 7 0 in Which the material is subjected to a calcining temperature. The chamber 70 may-bemade'of any suitable material capable of withstanding the temperatures employed. For example, it may be made of fire clay,-tile,or brick, or it may be made of a heat resisting metal. Chamber 7 O is connected directly with a source of heat '71 which may be an auxiliary furnace, havmg amixlng or combustion chamber, lnto co which a draft of diluting air or air to support combustion is supplied by means of lower 73. One furnace used by me had preheating passages in the furnace Walls with adjustable openings so as to give .thorough control of air inlets and give complete .tion 1s not necessarily followed in all cases combustion. A feeding mechanism 72 may discharge into said fan 7 3 to supply salts of alkali from metals, although such salts may also be introduced at any other point in the system, for example, at 68. In passing '77, which in turn discharge into a fan or impeller 78 which discharges into a fourth air separating chamber 54 by means of pipe 79. Fan or impeller 7 8 may have a means of admitting cold air thereto as indicated at 76 so as to further cool the recently calcined material discharged from chamber 53.

Chamber 54 discharges the finely divided cal-I cined mineral through a feeding mechanism. such as a tourniquet 84 into a storage bin or other suitable receptacle 85, from which such material may be withdrawn through means 86 for bagging or other disposition. The gases leaving the air separatin chamber 54 throughpipe means 80, 61101 gases containing exceedingly minute particles of mineraldnatte'r, are led into a suitable dust collecting or air separatin system, such as is indicated-at 82, and whicl ing dust collector in which the minute parti-- cles are retained and collected in the bottom of said collector in bin 83.

It is to bra-remembered that Figs. 1 and 2 are merely disagrammatic representations of the fundamental ideas embodied in my invention and that the angle at which the various pipe means connect the units maybe varied to a large degree, and the number or location of fans orimpellers may be changed 7 with the conditions encountered in practice.

For example in Fig. 2, the calcining chamber 70 may be placed vertically and the c alcined material discharged into a fireproof storage in which it is cooled .before being passed through air separating chamber 53 or 54 or both. The addition of salts of alkali metals during or before the calcining operainasmuch as a purely calcining operationon finely divided mineral matter may be accomplished without such salts. Furthermore,

the fans or impellers used in this invention 1 may be a stock i Ill? may readily accomplish a certain amount of milling or disintegration, particularly when i an easily reduced mineral, such as diatomaceous earth, is being treated. Whenever fans or Impellers are therefore specified they may be understood to function not only as means of blowing but also as secondary disintegrators, The fundamental idea of novelparatus into-a heated gas, passing such gas and disintegrated material into a second separating apparatus and circulating the partly spent gas containing dust from the second separating apparatus to the moist disintegrated material.

2. In a combined milling and heating process, the prevention of .dust loss by dis- -integrating material containing moisture,

passing such disintegrated material by pneumatic means into a separating chamber, discharging the dust free gas from such chamber into the atmosphere, discharging the milled material from such chamber into a current or" heated gas, conveying the milled material and gas to a second separating chamber and discharging the dust laden gas from such second chamber into the mois-' ture-containing material so as to conserve such dust.

'3. In a combined milling and heatin process employing dismtcgratmg apparatus, and primary and secondary air-separating c chambers, the circulation of partly spent heated gases containing dust from the secondary air separating chamber to the disintegrating apparatus so as to conserve such dust, and discharging dust free air from the primary air separating chamber.

4. In a combined milling and heating process, the prevention of dust loss by disintegrating diatomaceous earth containing moisture, passing such disintegrated diatomaceous earth by, pneumatic means into a separating chamber, discharging the dust free gas from such chamber into the atmosphere, discharging the milled diatomaceous earth from such chamber into a current of heated gas, conveying the milled diatomaceous earth and gas to a second separating chamber and discharging the dust laden gas from such second chamber into the disintegrated moist diatomaceous earth so as to conserve such dust. I

5. An apparatus for disintegrating, and drying minerals without loss of dust comprising a substantially enclosed disintegrator, pneumatic means of conducting disin-' tegrated mineral to an .airseparating chamber, gas discharge me n r m, ald, chamber retract and discharge means for disintegrated mineral from said chamber leading to a source of heated gas, means of conducting such heated gas and disintegrated mineral to a second separating chamber, and means for l a conducting the dust containing gases from suchchamber into the disintegrator to conserve such dust. v

6. An apparatus for disintegrating and drying diatomaceous earth containing moisture Without loss of dust comprising a substantially enclosed disintegrator, pneumatic means of conducting moist disintegrated dia-' tomaceous earth to an air separating chamber, gas discharge means from said chamber and discharge means for disintegrated diatomaceous earth fromsaid chamber leading to a source of heated gas, means of conducting such heated gas and disintegrated diatomaceons earth to a second separating chamber, and'means for conducting the dust containing gases from such chamber into the moist disintegrated material.

7. The herein described process of removing dust from dust laden air or, gases produced in the milling and heating of moist siliceous material and the like; consisting in millin the siliceous material, heating the mille materiaL-and returning the dry dust laden air or gases produced by such treatment into the moist material bein treated previous to the drying thereof, whereby the dust is deposited on and retained by the Wet or moist material.-

8. The herein described process of milling and drying moist diatomaceous earth, consistingin first disintegrating the raw diatomaceous earth, discharging the disintegrated diatomaceous earth into a suitable heater; and returning the dust laden gases orair produced by such treatment into the moistdiatpmaceou's earth being'treated before the latter reaches the heater.

9. In a combined milling and heating process, the prevention of dust loss by disintegrating moisture-containing diatomaceous earth, passing such disintegrated diatomaceous earth by pneumatic means into a separating chamber, discharging substantially dust-free gas from such chamber into the atmosphere, discharging the milled diatomaceous earth from such chamber into a current of gas at a temperature above 300 F., conveying the milled diatomaceous earth and gas to a second separating chamber by pneumatic means, and discharging the dust containing gas from such second chamber into the initial disintegrator containing moisture-contain ng material so as to. conserve such dust.

In testimony whereof I have hereunto subscribed my name this day of June,

MCKINLEY srocnron, 

